A former veterinary nurse who contracted bovine TB is believed to have caught the disease from badgers that strayed into her garden.
In a leaked report, scientists said badgers were the “likely source” of bovine TB infection in a woman in Cornwall last year.
Her daughter and her dog also tested positive for the disease.
The report, which has been submitted for possible publication in scientific journal Thorax, has raised fears over the threat of bovine TB to human health.
The report found the infection was the strain found circulating in cattle and badgers in south west Cornwall.
It concluded the most likely cause of infection was due to an encounter with badgers “known to inhabit her garden”.
A source from the NFU said the woman could have inhaled urine from infected badgers after touching grass or soil.
Bovine TB is known to spread to humans but occurrences are rare.
In 2006 and 2007, there were 20 cases nationally of bovine TB in humans, with eight of these in the south west of England.
Prior to this case, only two cases of bovine TB had been found in dogs in the past 20 years.